THREATENING TO CANCEL MY ORDER AND REFUSING TO DELIVER.

I bought JBL Tune 700BT Over ear Bluetooth Headphones yesterday on JBL Dare to listen website.I used Vouchers from McDonald's for discounts,my vouchers went through and my purchase was successfully paid and received an order number. This morning I received a rude email from the Connoisseur Electronic creative and Digital specialist who said that they will cancel my order because I used more than one voucher to make a purchase.Their system never declined my vouchers. Some online systems like takealot only takes one voucher when making a purchase and automatically declines another voucher if you try to redeem it. I cannot be treated like this for making a purchase on their website and successfully paying the outstanding amount. I'm just a customer,now they want to make their online system my problem. I'm waiting for my order Connoisseur Electronics my order was successfully paid and I have an order number.